The multi-layer material employed till now for the preparation of containers for beverages and foods such as fruit juices, milk or other, includes essentially a functional layer of cardboard which gives to the container mechanical properties, in particular rigidity, and, adhered to the cardboard, in some cases, a layer of a thin sheet of aluminum which is coated on the side which comes into contact with the beverage or food, with a polyethylene film or similar polymeric material.
Containers produced with such multi-layer materials are difficult to recycle due to the different chemical nature of the various layers.
The recyclability of the material forming a container for foods or beverages is a very important requisite both from the point of view of savings that recycling allows to be obtained and from an ecological aspect.
The possibility of having a recyclable material is a very important topic in the field.
Containers for beverages and liquids produced of polymeric materials exist but do not present characteristics of rigidity comparable to those of cardboard and for this reason they do not result in being suitable to produce rigid containers. The containers obtained with such materials come into the category of small sacks (pouches).
The attempt to obtain containers with the necessary rigidity using polymeric materials has failed until now.
The rigidity in the containers is in function of the thickness of the wall and more precisely varies with the cube of the wall thickness.
The use of polymeric materials such as polyolefins for the production of containers having sufficient rigidity would imply a thickness which is not economical and furthermore is not processable due to the difficulty in folding and sealing that is encountered in the phase of closing the container.
Another material such as foamed polystyrene is not employable due to its fragility when it is conformed into thin layers.
From the patent literature (U.S. Pat. No. 5,000,991) rigid laminates are known which are utilized for the preparation of thermoformed containers for victuals, formed of a sheet of foamed polyester material and a film of the same nature as the sheet, or of other polymeric material. Known from EB-A-836937 are semi-rigid laminates having a thickness of 0.5 to 1.5 mm and comprising a layer in polyester resin foam having density of 0.7 to 1 g/cm3 on which a layer of polymeric material having gas barrier properties, different from that of the layer in polyester foam, is adhered.
The laminates are utilized for the preparation by thermoformation of articles for packaging.
Mono and multi-layer materials comprising a layer of polymeric foam capable of being creased to form, by folding according to the pattern pressed on the material, the shape of the container, are not known in patent literature.
The capability of a polymeric foamed material, mono layer or multi-layer, to be pressed with a pattern set to develop by folding the shape of a container, and the foldability of the material according to such a pattern, constitute indispensable requirements for the production of containers for beverages and foods when using the creasing and folding technique.
A material is suitable for creasing if the pattern pressed on it remains stable over time and if in the stamping of such pattern there is no breakage which could impair the possibility of folding the material.
Moreover the material must be heat-sealable to render possible the closure of the container.